How is GFP used as a reporter gene to visualize protein location?

• A. GFP is used to increase the protein's expression levels.
• B. GFP is used to degrade unwanted proteins in the cell.
• C. GFP is fused to a protein of interest, and its fluorescence indicates the protein's location.
• D. GFP alters the protein's function to make it visible.

Answer: (C)